Alkanes are an important part of petroleum, the stability of alkanes under extreme conditions is of great significance to explore the origin of petroleum and the carbon cycle in the deep Earth. Here, we performed Raman and infrared (IR) spectroscopy studies of n-hexane and cyclohexane under high pressure up to ∼42 GPa at room temperature (RT) and high temperature (HT). n-Hexane and cyclohexane undergo several phase transitions at RT around 1.8, 8.5, 18 GPa and 1.1, 2.1, 4.6, 13, 30 GPa, respectively, without any chemical reaction. By using resistive heating combined with diamond anvil cell at pressure up to 20 GPa and temperature up to 1000 K, both n-hexane and cyclohexane decompose to hydrogenated graphitic carbon and n-hexane exhibits higher stability than cyclohexane. Our results indicate that hydrocarbons tend to dehydrogenate in the upper mantle, and the extension of carbon chains may lead to the formation of some unsaturated compounds and eventually transfer into graphitic products.

烷烃是石油的重要组成部分，烷烃在极端条件下的稳定性对探索石油的起源和深部地球的碳循环具有重要意义。在这里，我们进行拉曼和红外（IR）光谱法研究Ñ正己烷和环己烷在高压下达到〜42 GPA在室温（RT）和高温（HT）。Ñ正己烷和环己烷经历几个相变在RT 1.8左右，8.5，为18GPa和1.1，2.1，4.6，如图13所示，为30GPa，分别，而没有任何化学反应。通过用电阻加热用金刚石压腔合并在压力高达20GPa的和温度高达1000 K，既Ñ正己烷和环己烷分解氢化石墨碳和Ñ-己烷比环己烷具有更高的稳定性。我们的结果表明，碳氢化合物倾向于在上地幔中脱氢，碳链的延伸可能导致一些不饱和化合物的形成，并最终转移到石墨产物中。